Method for using windows of similar equivalence signatures (areas of presentation spaces) in assessing the similarity of sets of data

ABSTRACT

A method for finding sets of data (SDDs), which are similar to a target SDD, is invented. The method leverages a new category of signatures, called equivalence signatures, to characterize the SDDs and is applicable to all types of data that may be presented in two-dimensions. These signatures have the salient feature that, at worst, they change in a bounded manner when small changes are made to the SDDs and when used to find SDDs that are similar to a target SDDs, they allow for a significant reduction in the number of SDDs to be compared with the target. This is an improvement over the state of the art wherein the computational expensive process of performing a complete search against the entire corpus must be applied.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of PPA Ser. No. 60/883,001, filed Dec. 31, 2006 by the present inventor and PPA Ser. No. 60/882,838, filed Dec. 29, 2006 by the present inventor.

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to the identification and retrieval of digital data by a computing device.

2. Prior Art

A method for the discovery of a set of digital data (SDD), such as images, videos, and the like, that are organized for point-wise presentation in two-dimensions, that are similar to a target SDD is invented here. Formulae for the areas of the sheets swept out by the data are used as signatures that characterize equivalence classes of SDDs with the same or numerically close data. The method leverages these “equivalence signatures” to find SDDs that are similar to target SDDs and, separately and alternatively, find SDDs that are dissimilar from the target SDDs.

The definition of “similarity”, and thus the features and method used to compute it, is idiosyncratic to the retrieval application [O'Connor]. In the case of image retrieval [Gonzalez], methods using entropy, moments, etc. as signatures, have been invented [U.S. Pat. Nos. 5,933,823; 5,442,716]. Another invention [U.S. Pat. No. 7,246,314], uses closeness to a Gaussian model as a similarity measure for identifying similar videos.

The cost of implementing these methods is typically proportional to the product of the number of SDDs in the database with the cost of computing the distance between the target SDD and another SDD. The latter often [Raghavan] involves the computation of the projection angle between two vectors that represent the features (e.g., histogram of the text elements) of the SDDs. For large databases, this process can be both resource and time expensive. A two step method is required wherein, during the retrieval phase, definitely dissimilar SDDs are first weeded out thereby significantly reducing the number of candidates for similarity. This first step should be computationally inexpensive thus significantly reducing the resource requirements and latency in computing the results of the second step, the application of traditional features.

Intuitively, if two SDDs are similar, then they should be locally deformable into each other. For example, if two images are rescalings and/or rotations of each other, then the images are similar. This invention leverages results from String Theory to address this problem. In particular, we appeal to field theory representations for the areas of sheets swept out by the SDD when stepping through the presentation space. By construction, these volumes are invariant under reparameterizations of the presentation space and thus characterize equivalence classes of area preserving maps between the presentation and data spaces.

We interpret each SDD as a sampling of maps from an two-dimensional space, N; with coordinates, (θ¹, θ²) to an m-dimensional space, M, with coordinates σ^(A) (θ¹, θ²) or σ^(A)(θ) for short, for A=1, . . . , m and seek volume preserving equivalence classes of such maps. The cases where m≧n are considered. We label the lengths of the presentation space dimensions as L⁽¹⁾ and L⁽²⁾ or width and height.

Let the raw data, {tilde over (σ)}^(A)(θ), of each SDD be organized into m data planes, e.g., three YUV color planes of images, for presentation and let each plane have a maximum and minimum value for the data in that plane, {tilde over (σ)}_(max) ^(A) and {tilde over (σ)}_(min) ^(A), respectively. The maximum and minimum values of each of the two planes are used to normalize their data to new minimum and maximum values, σ_(max) ^(A) and σ_(min) ^(A) respectively, through the expressions:

$\begin{matrix} {{\sigma^{A}(\theta)} = {{\frac{\sigma_{\max}^{A} - \sigma_{\min}^{A}}{{\overset{\sim}{\sigma}}_{\max}^{A} - {\overset{\sim}{\sigma}}_{\min}^{A}}\left\lbrack {{{\overset{\sim}{\sigma}}^{A}(\theta)} - {\overset{\sim}{\sigma}}_{\max}^{A}} \right\rbrack} + \sigma_{\min}^{A}}} & {{Eqn}.\mspace{14mu} 1} \end{matrix}$

Additional normalizations of the SDD, such as scaling to a fixed width and height and the like, may also be performed.

If objects have been segmented from the SDD then the data for these objects are themselves SDDs. We henceforth refer to each segmented portion as a “SDD section” with its own map, σ.

For SDD sections for two-dimensional presentation where there are at least two planes of data, such as images or video frames, the expression for the equivalence signature resolves to the area of the sheet represented by the data [Kaku], namely

$\begin{matrix} {{\xi\lbrack\sigma\rbrack} \equiv {\int_{0}^{L_{1}}{\int_{0}^{L_{2}}\ {{\mathbb{d}\theta^{1}}\ {\mathbb{d}\theta^{2}}\sqrt{{\left( {\sum\limits_{A = 1}^{m}{\frac{\partial\sigma^{A}}{\partial\theta^{1}}\frac{\partial\sigma^{A}}{\partial\theta^{1}}}} \right)\left( {\sum\limits_{B = 1}^{m}{\frac{\partial\sigma^{B}}{\partial\theta^{2}}\frac{\partial\sigma^{B}}{\partial\theta^{2}}}} \right)} - \left( {\sum\limits_{A = 1}^{m}{\frac{\partial\sigma^{A}}{\partial\theta^{1}}\frac{\partial\sigma^{A}}{\partial\theta^{2}}}} \right)^{2}}}}}} & {{Eqn}.\mspace{14mu} 2} \end{matrix}$

SDD sections that have the same value for the equivalence signature will belong to the same equivalence classes under:

-   -   reparametrizations of the presentation space (e.g., warping of         the image)     -   rotations of the presentation space (e.g., rotating an image         from landscape to portrait)     -   resealing of the presentation space (e.g., changing the sizes of         images)     -   offsets in the data values (e.g., change in the brightness of         images)     -   replacing the data values with their mirrored values     -   global, orthogonal rotations of the planes into each other         separately and collectively. Proofs of these symmetries are         recounted in works such as Ref. [Kaku].

Consider two SDD sections, σ′^(A) (θ) and σ^(A)(θ) such that at each point, the difference between the values of the maps is ε^(A) (θ), ε^(A)(θ)=σ′^(A)(θ)−σ^(A)(θ)  Eqn. 3

For the two SDD sections to be similar we take ε^(A) (θ) to be small compared with σ^(A)(θ) so that terms of order ε²(θ) can be neglected. With this as a quantitative measure of similarity, we can assign bounds on the differences of the equivalence signatures via the functional difference: Δξ[σ;ε]≡ξ[σ+ε]−ξ[σ]  Eqn. 4

As ε^(A) (θ) is small, to a first approximation, Δξ[σ; ε] is a linear functional of ε^(A). We will exploit this henceforth.

For example, suppose we are interested in finding images the data values of whose color planes differ by no more than p percent at each pixel, then ε^(A) (θ)=pσ^(A)(θ) are used in the computation of Δξ[σ; ε]. Retrieval of similarity candidates proceeds by finding those images with values of ξ[σ], denoted as ξ[σ_(similar)], for which the following inequalities hold: |ξ[σ_(target)]−ξ[σ_(similar)]|≦Δξ[σ_(target);ε]  Eqn. 5

As an example for the reduction factor for the number of CPU cycles and other resources required in finding similar sections of SDDs in a corpus, assume for simplicity that the equivalences signatures of the SDD sections in the corpus are uniformly distributed in [ξ_(max), ξ_(min)]. If for a target SDD section, the choice of similarity lead to Δξ[σ; ε], the reduction in the number of secondary features to be compared is

$\begin{matrix} {f_{r} = \frac{\left( {{2\;\Delta\;{\xi\left\lbrack {\sigma;ɛ} \right\rbrack}} + 1} \right)}{\left( {\xi_{\max} - \xi_{\min} + 1} \right)}} & {{Eqn}.\mspace{14mu} 6} \end{matrix}$

In state of the art information retrieval methodologies, the feature vector which is used for each SDD section would have to be compared to all N_(c) feature vectors computed for the SDD sections in the corpus. Upon employing the method invented here as a precursor to the feature vector comparison, the number of feature vectors to be compared would be reduced to f, N_(c).

OBJECTS AND ADVANTAGES

The objects of the current invention include the:

-   -   1. computation of an equivalence signature for each SDD section         such that two SDD sections with equivalence signatures that         differ by more than a prescribed amount, will not be similar,     -   2. population of a database with the equivalence signatures,         secondary features and other meta data about the SDD,     -   3. use of the equivalence signatures for the identification of         those SDDs that are not similar to a target SDD,     -   4. use of equivalence signatures for the identification of those         candidate SDDs that may be similar to a target SDD,     -   5. use of the secondary features and other meta data for the         candidate similar SDDs in further analysis, such as feature         comparison, to determine the final set of similar SDDs, and     -   6. retrieval of the files containing the similar SDDs by means         of the meta data stored in the database.

The advantages of the current invention include:

-   -   1. a method for computing these signatures for data, such as         images and video frames, that have segmented components realized         in a two-dimensional plane with each point in the plane having a         plurality of values,     -   2. a quantifiable means for measuring similarity, and     -   3. the computational and resource expense of using feature         comparison methods to determine the similarity of SDDs is         reduced to a fraction given by a function of the change allowed         between similar data.

SUMMARY

In accordance with the present invention, a method for determining the similarity of sets of data uses the metric induced by the values of the data to compute an equivalence signature for each segmented component or section of sets of digital data (SDDs), and further uses the differences of the equivalence signatures of any two sections of a SDD as the measure of the similarity distance between sections of said SDDs. The output from this method can be used to significantly reduce the computational expense, time and resources required by a subsequent secondary feature comparison.

DRAWINGS Figures

In the drawings, closely related figures have the same numerically close numbers.

FIG. 1 is a block diagram of a computing device for calculating the equivalence signatures of a plurality of SDDs (targets) and finding previously analyzed SDDs that are similar to (or separately and alternatively not similar to) the target(s), according to one embodiment.

FIG. 2 is a block diagram of the modules and their interconnections, executed by the processing unit of the computing device in FIG. 1, in computing the equivalence signature of and determining the similarity of a plurality of SDDs to other SDDs, according to one embodiment.

FIG. 3 is a flow diagram illustrating the steps taken by the modules, in FIG. 2, to compute equivalence signatures of SDDs and adding them to a database, according to one embodiment.

FIG. 4 is a flow diagram illustrating the steps taken by the modules, in FIG. 2, to find other SDDs that are similar to a target SDD, according to one embodiment.

DETAILED DESCRIPTION Preferred Embodiment—FIGS. 1-4

A preferred embodiment of the method of the present invention is illustrated in FIGS. 1-4.

A SDD is represented as a set of integers (realized in a computing device as a set number of bits). Each SDD may be realized as the addition of layers of or concatenation of SDD sections. The entire SDD, or the resultant from the point-wise addition of or concatenation of all sections of the SDD, is also taken to be a section. Each point in said sections may have a plurality of integer values. For example, some images are composed of a set of layers of segmented objects with each pixel having three color values or one luminance and two color values.

To determine the similarity, or separately and alternatively non-similarity, of one or a plurality of SDDs with a plurality of SDDs, each SDD may be numerically characterized. For example, each section of the SDDs of a corpus of SDDs may be assigned an equivalence signature that has the property that small changes to the section of the SDD, which maintain similarity with the original section of the SDD, will not significantly change the equivalence signature.

As specified by Eqn. 2, the equivalence signature for each section of a SDD is given by the functional representation of the length of the path computed over the data of the SDD's section interpreted as a mapping between the presentation data and the space of data values. Once an equivalence signature is assigned to a section of a SDD, then a plurality of SDDs that are small deformations of the former SDD will have equivalence signatures that are within a bounded range of the equivalence signature of the former SDD as given by Eqn. 5. That range is computed based on configurable similarity threshold parameters that specify the point-wise allowed differences between similar sections of SDDs. Consequently, SDD sections that are candidates for similarity with a section of a target SDD can be identified, in a database, by requiring that the absolute value of the difference between the values of their equivalence signatures and that of the target's section be no more than the maximum allowed difference computed in terms of the target's data and the similarity threshold parameters. If a target SDD has N_(s) ^((T)) sections of which N_(s) ^((T)) (X) are similar to the sections of another SDD, X, then the degree of similarity of X to the target SDD is

$\frac{N_{s}^{(T)}(X)}{N_{s}^{(T)}}.$ The closer the degree of similarity to one, the more similar X is to the target SDD. SDDs in a database that are not similar to a target SDD will have a similarity degree of zero.

Operation Preferred Embodiment—FIGS. 1-4

In FIG. 1, an illustration of a typical computing device 1000 is configured according to the preferred embodiment of the present invention. This diagram is just an example, which should not unduly limit the scope of the claims of this invention. Anyone skilled in the art could recognize many other variations, modifications, and alternatives. Computing device 1000 typically consists of a number of components including Main Memory 1100, zero or more external audio and/or video interfaces 1200, one or more interfaces 1300 to one or more storage devices, a bus 1400, a processing unit 1500, one or more network interfaces 1600, a human interface subsystem 1700 enabling a human operator to interact with the computing device, and the like.

The Main Memory 1100 typically consists of random access memory (RAM) embodied as integrated circuit chips and is used for temporarily storing the SDDs, configuration data, database records and intermediate and final results processed and produced by the instructions implementing the method invented here as well as the instructions implementing the method, the operating system and the functions of other components in the computing device 1000.

Zero or more external audio and/or video interfaces 1200 convert digital and/or analog A/V signals from external A/V sources into digital formats that can be reduced to PCM/YUV values and the like. Video frames of YUV values at each two-dimensional point in the frame, are SDDs.

Storage sub-system interface 1300 manages the exchange of data between the computing device 1000 and one or more internal and/or one or more external storage devices such as hard drives which function as tangible media for storage of the data processed by the instructions embodying the method of this invention as well as the computer program files containing those instructions, and the instructions of other computer programs directly or indirectly executed by the instructions, embodying the method of this invention.

The bus 1400 embodies a channel over which data is communicated between the components of the computing device 1000.

The processing unit 1500 is typically one or more chips such as a CPU or ASICs, that execute instructions including those instructions embodying the method of this invention.

The network interface 1600 typically consists of one or more wired or wireless hardware devices and software drivers such as NIC cards, 802.11x cards, Bluetooth interfaces and the like, for communication over a network to other computing devices.

The human interface subsystem 1700 typically consists of a graphical input device, a monitor and a keyboard allowing the user to select files that contain SDDs that are to be analyzed by the method.

In FIG. 2, an illustration is given of the modules executing the method of the present invention on the processing unit 1500.

An equivalence signature is computed as in, 1500, for a SDD under the control of the Analysis Manager. First, the Analysis Manager 1550 instructs the Data Reader 1510 to read the SDD and return control to the Analysis Manager 1550 upon completion. Secondly, when control is returned by the Data Reader 1510, the Analysis Manager 1550 instructs the Data Preprocessor 1520 to process the output from the Data Reader 1510 and return control to the Analysis Manager 1550 upon completion. Third, when control is returned by the Data Preprocessor 1520, the Analysis Manager 1550 instructs the Signature Generator 1530 to process the output from the Data Preprocessor 1520 and return control to the Analysis Manager 1550 upon completion. Fourth, when control is returned by the Signature Generator 1530, the Analysis Manager instructs the Signature Database 1560 to record the output from the Signature Generator 1530, said Signature Database may write the output to a file by means of calls to the Operating System 1570, and return control to the Analysis Manager 1550 upon completion. The Analysis Manager 1550 then waits for the next request.

The Data Reader module 1510 reads the SDD from its storage medium such as a file on a hard drive interfaced to the bus of the computing device or from a networked storage device or server using TCP/IP or UDP/IP based protocols, and the like.

The Data Preprocessor module 1520 finds the start and end of each section in the SDD by finding the start layer markers in the data stream of the SDD. It also reads the headers of each SDD to determine if the header matches with configured values specifying if the SDD is to be treated as a two-dimensional presentation space.

In FIG. 3, a request to compute the equivalence signatures of a SDD is received 100 by the Signature Generator 1530. The Signature Generator first reads the configured maximum and minimum values to which to normalize the data in subsequent steps. Secondly, it pre-processes 102 the first section from the SDD by executing the following steps in sequence:

-   1) first, allocates a section buffer in main memory and partitions     it into planes that are offset from each other by the product of the     width and height of each plane, -   2) second, breaks each section into color planes where each     world-point of the data of the section is in one-to-one     correspondence with the world-point in each plane, -   3) third, for each color plane, sets the maximum value and minimum     value to the value of the data at the first point in the plane and     then sequentially reads the value of the data at each subsequent     point in the plane to see if that value is     -   a) larger than the current maximum value for the plane, in which         case it updates the current maximum value for the plane to the         value of the data at the current point, or     -   b) smaller than the current minimum value for the plane, in         which case it updates the current minimum value for the plane to         the value of the data at the current point, -   4) fourth, for each color plane, normalizes each data value read by     -   a) subtracting the configured maximum value for the plane from         said data value,     -   b) multiplying the result from step by the ratio of the         differences between the configured maximum and minimum values         for the plane and the difference between the maximum and minimum         values computed for the plane in step, and     -   c) adding the maximum value to form the normalized value,     -   d) said normalized value is then written to the section buffer, -   5) fifth 104, if there are m color planes in the section then the     equivalence signature is calculated as follows:     -   a) introducing and setting a variable, with name such as ES, to         zero,     -   b) processing loops over the values of y from y=0 to y=(H−1)         incrementing by one at each roll of the loop, where H is the         height of the two-dimensional data,     -   c) for each y, loops over the values of x from x=0 to x=(w−1)         incrementing by one at each roll of the loop, where W is the         width of the two-dimensional data,     -   d) for each x and y, setting the value of three variables, with         names such as h_(xx), h_(xy) and h_(yy), to zero and looping         over each of the m color planes and for each plane         -   i) reading the data values at (x; y), (x+1, y), (x, y+1) and             (x+1, y+1) from the plane and assigning it as the values of             the variables with names such as a σ_(x,y), σ_(x+1,y),             σ_(x,y+1), σ_(x+1,y+1), respectively,         -   ii) computing the difference of σ_(x+1,y) minus σ_(x,y) and             assigning the result to a variable with name such as at             d_(x)σ_(x,y),         -   iii) computing the difference of σ_(x,y+1) minus σ_(x,y) and             assigning the result to a variable, with name such as d_(y),             σ_(x,y),         -   iv) computing the product of d_(x)σ_(x,y) and d_(x)σ_(x,y)             and adding it to the value of h_(xx),         -   v) computing the product of d and d_(x)σ_(x,y) and             d_(y)σ_(x,y) adding it to the value of h_(xy)         -   vi) computing the product of d_(y)σ_(x,y) and d_(y)σ_(x,y)             and adding it to the value of h_(yy)         -   vii) continuing to loop over color planes until the last             color plane is reached at which point the square root of the             result, from the subtraction of the product of h_(xy) and             h_(xy) from the product of h_(xx) and h_(yy), is computed             and added to the value of the variable -   6) seventh 106, a new record is added to the Signature Database 1560     -   a) with the most significant half (MSH) of the key equal to the         value the variable ES, and the least significant half (LSHi) of         the key set to one plus the value of the largest LSH of the         other keys in the database which have a MSH equal to value of         ES, and     -   b) other fields containing the meta data about the section of         the SDD that was provided in the request at 100; such meta data         may include other signatures or features of the section of the         SDD, and the like.

The calculations of 102-108 are performed while looping over the remaining sections. When no more sections remain 110, a new record is added to the Signature Database 1560 with fields containing the keys of the record of each section of the SDD, the meta data about the SDD including the path or URL to the file containing the SDD, the data and time that the SDD was last written, a text description of the data in the SDD, the name of the source or author for the SDD, the policy for the use of the SDD, other signatures or features of the SDD, and the like.

In FIG. 4, a target SDD is provided in a request 200 to the Analysis Manager 1550 to find SDDs, that were previously analyzed and whose equivalence signatures are stored in records of the Signature Database 1560 that are candidates for similarity with the target. To with, the Analysis Manager 1550 instructs the Data Reader 1510, Data Preprocessor 1520 and Signature Generator 1530 in series as follows:

-   1) a dictionary, the dictionary of candidate similar SDDs, ordered     as the doublet (key of a SDD meta data record, count of appearance     of similar sections with said key of a SDD meta data record) is     initiated with all counts set to zero, -   2) the buffer of similarity difference data at each point in each     plane is populated from configuration data containing said     similarity difference data, -   3) a loop over each section in the target SDD is performed 202     -   a) the equivalence signatures for the section in the loop is         computed 204 as described by FIG. 3, with each equivalence         signatures so computed then stored as the value of the variable,         ES,     -   b) a second equivalence signature is computed 206 as described         by FIG. 3 and then stored as the value of the variable, ESPrime,         except that the value of the data at each point for each plane         is replaced by the sum of         -   (1) the value of the similarity difference data at the point             in the plane         -   (2) the value of the data at the point in the plane.     -   c) the minimum equivalence signature for a similar section is         computed 208 as the minimum of         -   (1) ESPrime, and         -   (2) twice the value of the variable ES minus the value of             ESPrime, and the value of said minimum equivalence signature             is assigned to the variable ESMin,     -   d) the maximum equivalence signature for a similar section is         computed 208 as the maximum of         -   (1) ESPrime, and         -   (2) twice the value of the variable ES minus the value of             ESPrime,         -   and the value of said maximum equivalence signature is             assigned to the variable ESMax,     -   e) a loop is performed over the signature records in the         Signature Database 1560 for which the MSH of keys of the records         is equal to or greater than the ESMin and less than or equal to         ESMax, from each of the signature records found, the key for the         meta data record of the SDD associated with the signature record         is extracted and the count of the corresponding entry in the         dictionary of candidate similar SDDs is incremented, -   4) the keys of the SDD meta data records appearing in the dictionary     of candidate similar SDDs are ordered by their appearance counts     from highest count to lowest, -   5) the meta data from each field in each record whose key is in the     dictionary of candidate similar SDDs is returned, by the Analysis     Manager 1550, ordered from most similar to less similar according to     the ordering in step.

Operation Additional Embodiments—FIG. 2

In a second embodiment, an equivalence signature is computed for a SDD as in 1500 through the pipelined steps: Data Reader 1510→Data Preprocessor 1520→Signature Generator 1530→Signature Database 1560 with the Data Reader 1510, Data Preprocessor 1520, Signature Generator 1530, and Signature Database 1560 performing the same function as in the preferred embodiment except that each module calls the succeeded module in the pipeline upon completion of their computation. In this second embodiment, the Analysis Manager is not invoked.

In a third embodiment, the similarity difference data is computed from the data of the target SDD by multiplying each data value by a number configured for each plane of data.

CONCLUSION, RAMIFICATIONS, AND SCOPE

Accordingly, the reader will see that the method invented here introduces novel features of an equivalence signature including that

-   -   1. it can be directly used to reduce by a factor, the set of         candidate SDDs that are to be further analyzed for similarity by         more computationally intensive feature comparison techniques         such as [U.S. Pat. Nos. 7,031,980; 5,933,823; 5,442,716] and a         similar reduction in the computing cycles and resources needed         to find SDDs can be obtained;     -   2. the difference between the equivalence signatures of two         non-equivalent SDDs is bounded;     -   3. it applies to multiple types of digital media.

The present invention has been described by a limited number of embodiments. However, anyone skilled in the art will recognize numerous modifications of the embodiments. It is the intention that the following claims include all modifications that fall within the spirit and scope of the present invention. 

1. A method comprising: a) computing the difference of the data value at each position in the plane and the data value at each position shifted by one in the x-direction in the plane, squaring the result and summing over said results for each plane to form the value of the xx entry of the metric at the (x, y) position, b) computing the difference of the data value at each position in the plane and the data value at each position shifted by one in the y-direction in the plane, squaring the result and summing over said results for each plane to form the value of the yy entry of the metric at the (x, y) position, c) multiplying the difference of the data value at each position in the plane and the data value at each position shifted by one in the x-direction in the plane with the difference of the data value at each position in the plane and the data value at each position shifted by one in the y-direction in the plane, and summing over said results for each plane to form the value of the xx entry of the metric at the (x, y) position, d) computing the result for the determinant of the metric at the (x, y) position as the result of the product of the xx entry of the metric and the yy entry of the metric minus the result of the square of the xy entry of the metric, e) computing the square root of the determinant of the metric at the (x, y) position, f) adding the result from the previous step to the result from the previous iteration of this inner most loop, if this is not the first iteration of said inner most loop, to form the loop result for the inner most loop, g) upon completion of the loop over the x-positions performing the next iteration over the loop of y-positions, h) upon completion of the loop over the y-positions assigning the final result for the loop result for the inner most loop as the value of the equivalence signature.
 2. The method of claim 1, comprising a means for arranging the data values into planes with specified starting addresses and lengths of each presentation dimension for each plane wherein the i^(th) plane consists of the set of the i^(th) data values at each point.
 3. The method of claim 1, wherein computing an equivalence signature of a section of digital data further comprises normalizing the data values of each plane by any of a plurality of methods including linearly mapping the data of each plane individually to fixed maximum and minimum values using slope-offset formulae.
 4. A computer-implemented method comprising: a) receiving, into a provided memory readable and writable by a provided CPU, one or more sets of digital data (SDD) which can be presented in two-dimensions, each set comprising: i) data values organized in sequential addresses or at set intervals of addresses, ii) the number of data values per data point, iii) a specified starting address, and iv) a specified number of data points, called the length, in each presentation dimension; b) using a processor to compute a numerical similarity signature, referred to as the equivalence signature as the volume of the presentation space, c) computing a similarity distance between any two sets of digital data as the absolute value of the difference of their equivalence signatures, d) persisting said equivalence signature for said input SDD by means of a database for storing a record for each of the sections of said input set of digital data, if said record is not already present in the database and the database is configured to store said records; and e) querying the database for sections of the sets of digital data that are candidates for similarity with said one or more target sections of the said input set of digital data, wherein, for images, video frames, graphics and other digital data that may be presented in two-dimensions, computing an equivalence signature as the area of the presentation space of normalized digital data, further comprises: looping over each y-position, from the first y-position to the second to last y-position, and over each x-position, from the first x-position to the second to last x-position, and for each position, the area density is computed as follows, a) computing the difference of the data value at each position in the plane and the data value at each position shifted by one in the x-direction in the plane, squaring the result and summing over said results for each plane to form the value of the xx entry of the metric at the (x, y) position, b) computing the difference of the data value at each position in the plane and the data value at each position shifted by one in the y-direction in the plane, squaring the result and summing over said results for each plane to form the value of the yy entry of the metric at the (x, y) position, c) multiplying the difference of the data value at each position in the plane and the data value at each position shifted by one in the x-direction in the plane with the difference of the data value at each position in the plane and the data value at each position shifted by one in the y-direction in the plane, and summing over said results for each plane to form the value of the xx entry of the metric at the (x, y) position, d) computing the result for the determinant of the metric at the (x, y) position as the result of the product of the xx entry of the metric and the yy entry of the metric minus the result of the square of the xy entry of the metric, e) computing the square root of the determinant of the metric at the (x, y) position, f) adding the result from the previous step to the result from the previous iteration of this inner most loop, if this is not the first iteration of said inner most loop, to form the loop result for the inner most loop, g) upon completion of the loop over the x-positions performing the next iteration over the loop of y-positions, h) upon completion of the loop over the y-positions assigning the final result for the loop result for the inner most loop as the value of the equivalence signature.
 5. The method of claim 4, comprising a means for creating and writing a record, in said database, for each section in each set of the said input sets of digital data, comprising, a) a key, i) the most significant half of whose value, is the equivalence signature of said section in the set of digital data, and ii) the least significant half of whose value is the sequential count, starting at zero, of sections of digital data with said equivalence signature and whose equivalence signatures were previously written to the database, b) one or more fields including a field storing the value referencing the medium wherein said set of digital data is stored, and c) one or more fields including secondary feature data, for said planes or set of digital data, and d) other fields containing meta data about said set of digital data.
 6. The method of claim 4, wherein a storage identifier comprises the location of a file containing a set of digital data along with the starting position of said data set in the file and the length of the data comprising said set.
 7. The method of claim 4, further comprising a means for writing a record including assigning the key, the most significant half of whose value is the equivalence signature for a section in the set of digital data.
 8. The method of claim 4, further comprising a means for reading a plurality of records and for each of the records extracting the equivalence signature of a set of digital data as the most significant half of the key of the record and extracting the fields, containing secondary features as well as the meta data, including the storage identifier, from the record.
 9. The method of claim 4, further comprising a means for retrieving, from said database, a plurality of records for which the most significant half of the values of the keys of the records are equal to a specified equivalence signature of a said target sections.
 10. The method of claim 4, further comprising a means for retrieving from said database a plurality of records with the most significant half of the values of the keys being within a range of equivalence signatures.
 11. The method of claim 4, further comprising the selection of a target section of said input set and the computation of a lower and upper bound on the values of the equivalence signature such that any section of sets of digital data with equivalence signatures that are less than the lower bound or greater than the upper bound will not be similar to the target section and all other sections of sets of digital data recorded in the database will be candidates for sections of sets of digital data that are similar to the target section, with a) the lower bound given by the equivalence signature of the target section minus the absolute value of an equivalence signature delta for the target section, and b) the upper bound given by the equivalence signature of the target section plus the absolute value of an equivalence signature delta for the target section.
 12. The method of claim 11, further comprising a means of extracting, from said database, a plurality of records with keys such that the most significant half of each key is equal to or greater than said lower bound and equal to or less than said upper bound.
 13. The method of claim 11, wherein said equivalence signature delta is computed as the equivalence signature of said target section of a set of digital data minus a second equivalence signature for said target section with data values resealed and shifted by set constants for each plane specifying the maximum scaling and shifting of the data values at each data point in a plane in order for the plane so altered to still be considered similar to the corresponding unaltered plane.
 14. The method of claim 13, further comprising a means for specifying the maximum scaling and shifting of the data values at each data point in a plane in order for the section so altered to still be considered similar to the corresponding unaltered section.
 15. The method of claim 4, further comprising a means to return to a user of the method, a) the difference between the value of an equivalence signature of said target section and the most significant halves of the keys returned by said database; and b) the meta data from each field in the records identified by said keys.
 16. The method of claim 4, further comprising calculation of and sorting of a list of differences, between the equivalence signature of said target pair of and the values of the most significant halves of the keys of the records of the candidates for similar digital data, from smallest to largest values of said differences along with a means for returning to the user of the method, the meta data from the records ordered by the sorted differences.
 17. A computer-implemented method comprising: a) a means for receiving, into a provided memory readable and writable by a provided CPU, one or more sets of digital data which can be presented in two-dimensions, each set comprising i) data values organized in sequential addresses or at set intervals of addresses, ii) the number of data values per data point, iii) a specified starting address, and iv) a specified number of data points, called the length, in each presentation dimension; b) a means for computing a numerical similarity signature, referred to as the equivalence signature as the volume of the presentation space, c) a means for computing a similarity distance between any two sets of digital data as the absolute value of the difference of their equivalence signatures, d) a means for computing a persistence of said equivalence signature for said input sets digital data by means of a database for storing a record for each of the sections of said input set of digital data, if said record is not already present in the database and the database is configured to store said records, e) a means for querying the database for sections of the sets of digital data that are candidates for similarity with said one or more target sections of the said input set of digital data; and f) a means for comparing a set of secondary features provided with a target section of a set of digital data against the secondary features for similar sections of digital data whose records are in said database; wherein, for images, video frames, graphics and other digital data that may be presented in two-dimensions, computing an equivalence signature as the area of the presentation space of normalized digital data, further comprises: looping over each y-position, from the first y-position to the second to last y-position, and over each x-position, from the first x-position to the second to last x-position, and for each position, the area density is computed as follows, a) computing the difference of the data value at each position in the plane and the data value at each position shifted by one in the x-direction in the plane, squaring the result and summing over said results for each plane to form the value of the xx entry of the metric at the (x, y) position, b) computing the difference of the data value at each position in the plane and the data value at each position shifted by one in the y-direction in the plane, squaring the result and summing over said results for each plane to form the value of the yy entry of the metric at the (x, y) position, c) multiplying the difference of the data value at each position in the plane and the data value at each position shifted by one in the x-direction in the plane with the difference of the data value at each position in the plane and the data value at each position shifted by one in the y-direction in the plane, and summing over said results for each plane to form the value of the xx entry of the metric at the (x, y) position, d) computing the result for the determinant of the metric at the (x, y) position as the result of the product of the xx entry of the metric and the yy entry of the metric minus the result of the square of the xy entry of the metric, e) computing the square root of the determinant of the metric at the (x, y) position, f) adding the result from the previous step to the result from the previous iteration of this inner most loop, if this is not the first iteration of said inner most loop, to form the loop result for the inner most loop, g) upon completion of the loop over the x-positions performing the next iteration over the loop of y-positions, h) upon completion of the loop over the y-positions assigning the final result for the loop result for the inner most loop as the value of the equivalence signature.
 18. The method of claim 17, further comprising the comparison, of said set of secondary features provided with said target section, against the secondary features for said similar sections of sets of digital data found by querying the database and returning the list produced by the comparison of the secondary features as the final list of sections of sets of digital data that are similar to said target section. 